As a method of controlling a radiation treatment apparatus, tracking irradiation has been proposed and practically applied (for example, Patent Document 1). The aforementioned tracking irradiation is a method in which positional information on a particular site (a tumor or the like) moving due to breathing and the like is acquired in real time and the radiation treatment apparatus is controlled such that the radiation treatment apparatus continuously irradiates the particular site with radiation. As the radiation treatment apparatus intensively irradiates the particular site with radiation through tracking irradiation, it is possible to ensure a radiation dosage at the particular site and to reduce the radiation dosage at surrounding sites.
As a method of acquiring positional information on a particular site when performing tracking irradiation, there is a method of detecting a position of a marker provided on a body surface or inside a body and calculating the positional information on the particular site from positional information on the marker.